Started stripping down a 25cc Homelite, it's one of those reconditioned leaf blowers, and noticed something odd about the exhaust port.

After removing the muffler for gutting, I noticed a small (approx. 1/8" dia.) hole in the cylinder, just above the exhaust port, that leads to the top inside of the cylinder, just above the piston's tdc. The muffler has a hole that lines up with it and apparently allows exhaust to bleed off into the inside of the muffler. There is a lot more compression with it plugged. Do all Homeys have this hole, and should it be blocked of left open to feed into the muffler?

Kiv

Looks like I found the answer to my own question!

Here's the info on the mystery hole in the cylinder:

"Homelite hop up: Tip #5

Remove your exhaust. Above the exhaust port is a useless hole into your engine. Run a 10-32 tap into it. use some JB Weld or other suitable epoxy and fill the inner part of the hole. Then thread a set screw into it to push some of the epoxy out and into the cylinder. Let it set and grind or cut it flush. You have now violated the State of Californias smog control act. Don't you feel better? :-)



This hole lets exhaust into the new fresh charge of fuel in the cylinder, thus diluting it. Bad for performance."

Kiv

KIV,
Don't run the tap into the cylinder at all or you'll have a surprise when you try to turn the engine through a compression cycle.

Enjoy,

Jim

kiv,

where did you find your tips on converting your Homelite? I am in process of tearing one down.

Thanks,
Zip

It used to be a decompressor for easier starting.

Try this link:

http://members.aol.com/meljohn999/Homelite-Hop-Up/

It's a boat site but contains a lot of good info on Homelites. Here's another really good one:
http://testfly.0catch.com/homelite/homelitemain.html

and another:
http://www.shark-racing.com/Ingles/T...Tecnicaing.htm

Here's a well-illustrated guide to carb adjustments:

http://www.whobbies.com/faqs.htm#12

Kiv

I plugged those holes on my Homelite 25s with set screws. I did not run the tap all the way through and you must be VERY careful not to let any metal chips fall in. You can blow air in through the spark plug hole to make sure they all come out. I've done it on three of those engines and the compression goes up considerably. They are very easy to start and have good power for a plane that's 14# or less. If you get the bigger carb from somebody like Carrprecision you'll get even more power and it will swing an 18-6 prop.

Jim

The hole on the exhaust side of the cylinder was for exhaust gas recirculation (EGR) for a pollution situation.

The decompression valve was on the intake side of the cylinder on the electric start models. This is a 1/8" npt threaded hole that you put a pipe plug into for model airplane use. The non electric start versions rarely even have a boss for the hole on the intake side.

The electric start ones had a 12v speed 400 type motor as the starter. They were not the most successful venture that Homelite ever made. They were rather rare.

Jim